Documents transmitted by facsimile or reproduced by copying machines often contain both mixture of characters and photographs, i.e., character and half tone areas. When it is attempted to simply record density signals resulting from reading such documents, images tend to shade off because of the deterioration of the high spatial frequency of an optical reader. Consequently, a half tone generating process such as the "dither" pattern process has been applied to the density signal corresponding to the document to eliminate blur in the image.
However, when the half tone generating process is applied to the density signal corresponding to the document, the problem is that fine lines in the character area tend to increasingly shade off even though the blur in the half tone area is to some extent eliminated.
A known image processing method employs a special discrimination circuit to distinguish between character and half tone areas, applying a border emphasizing process to the half tone area to correct a blur in the image and applying a binary process to the character area to correct blurred fine lines. The special discrimination circuit used to distinguish between the character and half tone areas in the above method has posed a problem in that the hardware tends to be large in scale.